Was the PocketBook in the video doing full refresh or partial refresh? It seemed to me that it was on the setting that only does full refresh every 5 pages. Its especially noticeable during the "Reading FB2" section of video 2 at 4:20 to 5:00.
The M90 can be seen making the full "flashing" page turn the whole time but the PocketBook makes non flashing turns until 4:57ish when it finally does a full black flash turn- which is the same speed as the M90 turn at that time stamp.
If the M90 was in this quick turn mode or the PocketBook was set to "Full Page Update-Always" then i believe the speed would be the same.
In the next sequence this is proven actually. The quick turn settings are not applied when reading DJVU material and you can see the page turns are of similar speed.
Clearly, though, the code is not optimized yet. The part in video one where it shows the M90 taking longer to turn zoomed pages than not zoomed pages. That's never happened in 6 inch device firmware builds that I remember. Its a matter of page buffering, Im sure that will get worked out in subsequent builds.